sedimentary
Chert (including varieties like Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale); Color: White, tan, yellow, or grey (in this specimen); Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- White, tan, yellow, or grey (in this specimen)
- Luster
- Waxy to dull
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale); Color: White, tan, yellow, or grey (in this specimen); Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed by the precipitation of silica from groundwater or within maritime sediments. Often found as nodules in limestone or chalk beds. Most specimens date from the Paleozoic or Mesozoic eras.
Uses & applications
Historically used for stone tools (arrowheads, knives) due to its sharp conchoidal fracture. Modern uses include road surfacing, jewelry (as jasper/agate), and fire-starting flint.
Geological facts
Chert is so hard it can scratch glass and steel. It was one of the most vital resources for prehistoric humans, allowing for the creation of durable, razor-sharp edges.
Field identification & locations
Identify in the field by its smooth, shell-like (conchoidal) fracture and its ability to spark against steel. Commonly found in creek beds or eroding out of limestone cliffs.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary